Three-dimensional (3D) printing is a process for making objects under computer control. Often, the objects are made sequentially by forming multiple layers of material that are joined together to form a 3D object having desired dimensions. A variety of materials can be used, including metal, ceramic, or polymeric materials. 3D printing systems can vary in their methods of forming the multiple layers, such as by melting, sintering, softening, hardening, or liquifying. The quality of a 3D object can depend on the processing conditions for printing the 3D object. For example, the type of material, the temperatures used to perform the joining, as well as atmospheric conditions surrounding the 3D object during its formation, which may influence characteristics, such as the shape, roughness, and porosity, of the 3D object. Currently needed are improved 3D printing systems and methods for forming high quality 3D objects, at a competitive cost.